Corrosion inhibitor



United States Patent Olhce 3,5 14 ,41 1 Patented May 26, 1970 ABSTRACT OF THE DISCLOSURE A pickling composition for the treatment of ferrous metals consisting of an aqueous inorganic acid, and including a 5-substituted-S-quinolinol as a corrosion inhibitor therein.

The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention is directed to a composition and method for the treatment of ferrous surfaces. More particularly the invention is directed to the utilization of novel 5-substituted-8-quinolinole as corrosion inhibitors 11 the presence of an aqueous acid solution to clean ferrous surfaces.

Iron and steel become coated with surface impurities, e.g., oxide scale in the course of manufacture. These surface impurities constitute a detriment in the further manufacture of the iron and steel. An usual method of scale or impurity removal involves the immersion of the metal in a pickling bath composed of an aqueous solution of inorganic acids such as hydrochloric, sulfuric, phosphoric and the like. It is a common practice to add to the pickling solutions additives or inhibitors to prevent corrosion and to reduce hydrogen embrittlement of the ferrous base which is a condition resulting from the dissolution of the metal and absorption of the liberated hydrogen by the ferrous base. Various organic bases containing nitrogen have been utilized as corrosion inhibitors. U.S. Pats. 2,606,873 and 2,814,593 disclose the utilization of quinoline and certain quinoline derivatives. However the utilization of the prior art quinoline compounds presented certain drawbacks. The prior art compounds do not exhibit entirely satisfactory corrosion inhibiting properties when used alone and therefore must be used in compositions containing an additional surface active agent. The presence of the active surfacing agent often contributes to undesirable foaming of the pickling solution.

The novel corrosion inhibitors utilized in the present composition, which are the subject of co-pending application 662,562 filed .Aug. 17, 1967, are derivatives of 8- quinolinol having an oxygenated side chain of the structural formula:

CHzO (CH2CH20)nR wherein R is selected from the group consisting of hydrogen and an alkyl radical containing from 1 to 20 carbon atoms, and n represents an integer from 1 to 4.

In practice, the novel derivatives of S-quinolinol are prepared by reacting 5-chloromethyl-S-quinolinol hydrochloride with a hydroxy-compound of the formula HO(CH CH O),,R wherein R and n have the significance defined above. Representative hydroxy-compounds are: ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol and the monoalkyl ethers such as ethylene glycol monoalkyl ether, diethylene glycol monoalkyl ether; triethylene glycol monoalkyl ether and tetraethylene glycol monoalkyl ether, wherein the alkyl radical is methyl ethyl, propyl, butyl, tridecyl, octadecyl and the like. As an illustration, the reaction proceeds as follows:

R a r W HO(CH2CH2O),,R

so-zoofo Representative S-substituted-S-quinolinol compounds include: 5-(2-hydroxyethoxymethyl)-8-quinolinol, 5-(7-hydroxy 2,5 dioxaheptyl)-8-quinolinol, S-(Z-methoxyethoxymethyl) 8 quinolinol, 5-(2,5,8-trioxanonyl)-8- quinolinol and 5-(2,5,8,1l-tetroxadodecyl)-8-quinolinol.

It is an object of the invention to provide and disclose an improved novel pickling composition for ferrous metals.

It is a further object of the invention to provide and disclose a pickling composition comprising novel 5-substituted-S-quinolinols and an inorganic acid.

It is a further object of the invention to provide and disclose a stable pickling composition comprising novel 5-substituted-8-quinolinols and an inorganic acid.

It is a further object of the invention to provide and disclose a process for pickling ferrous metals utilizing a composition comprising novel-5-substituted-8-quinolinols and an inorganic acid.

Other objects and a fuller understanding of the invention may be ascertained from the following description and claims.

The corrosion inhibitors of the present invention are more effective corrosion inhibitors than the parent compounds quinoline and 8-quinolinol. The beneficial range is between 10 to 500 milligrams of inhibitor per 50 milliliters of the pickling solution.

Experimentation was conducted comparing the corrosion inhibiting properties of the prior art compounds, i.e., quinoline and quinolinol, with the novel 5-substituted-8-quinolinols. The pickling compounds was prepared by dissolving a 50 milligram sample of the corrosion inhibitor in 50 milliliters of 4.8 N hydrochloric acid. A conventional 2 /2" by 2 /2" test strip of cold rolled steel, previously cleaned in accordance with military specification (Mil-A-13528-24 June 54), was immersed in the composition maintained at room temperature for a period of minutes. The steel panels were then removed from the test solution; rinsed with Water; dried with paper; rubbed with celite; washed with water and then alcohol; air dried and reweighed. The loss in weight, expressed as percent weight loss, is set forth in the table below. Run #1 was conducted identical to Runs 2 to 8 except that no inhibiting material was added to the test solution.

TABLE Percent wt. loss As indicated by the experimentation conducted above, the novel derivatives of 8-quinolinol have superior corrosion inhibiting properties when utilized with an inor- 3 ganic acid than the prior art compounds, i.e., quinoline and S-quinolinol.

Although I have described my invention with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in regard to components and proportions thereof may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

Having described my invention I claim:

1. A pickling composition for ferrous metals consisting essentially of: an aqueous inorganic acid selected from the group consisting of hydrochloric, sulfuric and phosphoric acids, and containing an amount sufficient to inhibit corrosion, a compound of the formula:

wherein R is selected from the group consisting of hydrogen and an alkyl radical containing from 1 to 20 carbon atoms, and n represents an integer from 1 to 4.

2. A pickling composition in accordance with claim 1 wherein the corrosion inhibitor consists of 10 to 500 miligrams of material per 500 milliliters of pickling solution.

3. A pickling composition in accordance with claim 1 wherein the corrosion inhibitor is 5-(2-hydroxyethoxymethyl) -8-quinolin0l.

4. A picking composition in accordance with claim 1 wherein the corrosion inhibitor is 5-(7-hydroxy-2,5-dioxaheptyl -8-quinolinol.

5. A pickling composition in accordance with claim 1 wherein the corrosion inhibitor is S-(Z-methoxyethoxymethyl) -8-quinolinol.

6. A pickling composition in accordance with claim 1 lHzo (CHzCHzOhR wherein R is selected from the group consisting of hydrogen and an alkyl radical containing from 1 to 20 carbon atoms, and wherein n represents an integer of from 1 to 4.

9. A process in accordance with claim 8, wherein the corrosion inhibitor consists of 10 to 500 milligrams of material per 500 milliliters of pickling solution.

References Cited UNITED STATES PATENTS 2,606,873 8/1952 Cardwell et a1. 252148 2,814,593 11/1957 Beiswanger et al. 252-148 X 2,948,680 8/1960 Fields 252392 X MAYER WEINBLATT, Primary Examiner A. I. RADY, Assistant Examiner US. Cl. X.R. 

